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Re: gfortran question about optional subroutine arguments
Mark Hounschell wrote:
On 03/14/2013 10:03 AM, Tim Prince wrote:
On 3/14/2013 9:39 AM, Mark Hounschell wrote:
When I use -std=f95 this fortran77 code will not compile. Many
different complaints but the most serious are normal variable
declarations:
INTEGER*8 TOTTIME(0:MAXTASK) ! Task total exec time (
Error: Nonstandard type declaration INTEGER*8 at (1)
[...]
No I'm not hoping to amend any standard. I have been using different
vendors flavours of fortran 77 since the mid 70s. This is how it's done
on every one I ever used. I assumed it was standard and can hardly
believe it isn't.
No, it is not in the Fortran standard; however, INTEGER*8, REAL*8 and
COMPLEX*16 are very common vendor extensions. Thus, with default options
(= -std=gnu), it is supported. Only if you explicitly ask for Fortran 95
conformance checks, it is rejected.
The point is, Tobias said that anything that builds using -std=legacy
should also build using -std=f95.
That's not what I meant. Rather the other way around:
Every program which builds with -std=f95 also build with -std=f2008,
every program which builds with -std=f2008 also builds with -std=gnu
(the default), and if it builds with -std=gnu, it also builds with
-std=legacy.
In addition, any* valid Fortran 66 or Fortran 77 program builds with
-std=f95 (or -std=f2003 or ...). Except that many such programs aren't
standard conform as they use vendor extensions.
If the program uses a vendor extension, you might need -std=gnu or
-std=legacy. But it only helps if a certain vendor extension is supported.
Regarding INTEGER(8): Fortran 95's intrinsic types support the syntax
REAL(kind=<constant integer expression>) :: ...
Many compilers use the byte-size for the number, e.g. INTEGER(8) for an
8-byte integer. However, using "8" directly is even less portable than
INTEGER*8. One should better use it by selected_real_kind() or via a
pre-defined constant such as real64. In any case, it makes it easier to
change the precision of the code by changing a single constant in some
module.
Tobias
* With the possible exception with -std=f95/f2003/f2008 for features
which were deleted in Fortran 95. (Maybe the compiler also only warns
for those.)